fix: wrong URL being reffered on README

On the instructions on how to verify the provenance, we were reffering
to the instructions on how to do so, but linking to the wrong URL.

Signed-off-by: Diogo Teles Sant'Anna <diogoteles08@gmail.com>

README.md

@@ -309,7 +309,7 @@ process](https://github.com/sigstore/.github/blob/main/SECURITY.md).
 ### SLSA Provenance
 This project emits a SLSA provenance on it's release! This enables you to verify the integrity
 of the downloaded artifacts and ensured that the binary's code really comes from this source code.
-To do so, please follow the instructions [here](https://github.com/urllib3/urllib3/blob/main/.github/workflows/publish.yml).
+To do so, please follow the instructions [here](https://github.com/slsa-framework/slsa-github-generator#verification-of-provenance).
 
 
 ## Info